Figure 4.

Cell-specific genetic interaction between Gα_S(gf) and twk-7 in GABAergic motor neurons. (A) The bending frequencies, (B) velocities, and (C) bending-amplitude-to-body-length ratios during spontaneous crawling are shown. (D) Representative pictures of worms during stimulated forward crawling. The arrows indicate the rescue effect on the bending amplitude of worms with a twk-7(null) background expressing the KIN-2(G³¹⁰D) protein in GABAergic motor neurons. (E) The corresponding amplitude-to-body-length ratios of stimulated animals. Wild-type animals reduced their amplitudes to the level of spontaneously crawling kin-2(cau1) and twk-7(null) single and double mutants. The amplitudes of these animals were not affected by stimulation. (F) The time that worms spent crawling forward (f), crawling backward (b), or dwelling (d) and (G) the straightness rates during spontaneous crawling are shown. Overexpression of wild-type TWK-7 altered the locomotion phenotypes in all genetic backgrounds. In contrast, the effect of dominant-negative KIN-2(G³¹⁰D) expression depends on the genetic background. The locomotion phenotypes of hyperactive kin-2(cau1) animals are reversed by the overexpression of KIN-2(G³¹⁰D). The locomotion phenotypes of twk-7(null) and twk-7,kin-2 double mutants are decisively not affected by KIN-2(G³¹⁰D) expression. The (H) spontaneous BBCF and (I) crawling velocities of kin-2(cau1), gsa-1(ce94), and pde4(ce268) mutants and the corresponding transgenic worms overexpressing wild-type TWK-7 in cholinergic or GABAergic motor neurons. For comparative reasons, data for N2 wild-types and twk-7(null) animals are shown. The effect of GABAergic neuron-specific overexpression of the wild-type form of TWK-7 or of the dominant-negative KIN-2(G310D) protein on locomotor activity and locomotion behavior was investigated in worms with different genetic backgrounds [wild-type, twk-7(null), kin-2(cau1), and twk-7(null), kin-2(cau1)]. All values in (A and B) and (F–I) represent the mean (± SEM) of at least N ≥ 3 independent experiments involving n ≥ 30 never-starved animals. For the measurement of wave parameters in (C) and (E), N = 3 independent experiments with n = 15 worms per trial were evaluated. *P < 0.05, **P < 0.01, and ***P < 0.001 (Student’s t-test). Dotted lines indicate the wild-type level. BBCF, body-bending crawling frequency; GABA, γ-aminobutyric acid.